Real time dynamics of Gating-Related conformational changes in CorA

CorA, a divalent-selective channel in the metal ion transport superfamily, is the major Mg(2+)-influx pathway in prokaryotes. CorA structures in closed (Mg(2+)-bound), and open (Mg(2+)-free) states, together with functional data showed that Mg(2+)-influx inhibits further Mg(2+)-uptake completing a regulatory feedback loop. While the closed state structure is a symmetric pentamer, the open state displayed unexpected asymmetric architectures. Using high-speed atomic force microscopy (HS-AFM), we explored the Mg(2+)-dependent gating transition of single CorA channels: HS-AFM movies during Mg(2+)-depletion experiments revealed the channel’s transition from a stable Mg(2+)-bound state over a highly mobile and dynamic state with fluctuating subunits to asymmetric structures with varying degree of protrusion heights from the membrane. Our data shows that at Mg(2+)-concentration below K(d), CorA adopts a dynamic (putatively open) state of multiple conformations that imply structural rearrangements through hinge-bending in TM1. We discuss how these structural dynamics define the functional behavior of this ligand-dependent channel.